Elastic behavior pressure effects

There is evidence that ozone has a delayed effect on elastic behavior. Excised lungs of rabbits that were unilaterally exposed to ozone at 1.0 ppm for 3 h and then allowed to breathe ambient air for up to 2 weeks showed a depression in the volume-pressure curves. This change was present during most of the postexposure test period. The mechanism underlying this response was not determined. ... 

Nylon-11. Nylon-11 [25035-04-5] made by the polycondensation of 11-aminoundecanoic acid [2432-99-7] was first prepared by Carothers in 1935 but was first produced commercially in 1955 in France under the trade name Kilsan (167) Kilsan is a registered trademark of Elf Atochem Company. The polymer is prepared in a continuous process using phosphoric or hypophosphoric acid as a catalyst under inert atmosphere at ambient pressure. The total extractable content is low (0.5%) compared to nylon-6 (168). The polymer is hydrophobic, with a low melt point (T = 190° C), and has excellent electrical insulating properties. The effect of formic acid on the swelling behavior of nylon-11 has been studied (169), and such a treatment is claimed to produce a hard elastic fiber (170). 

Melt Viscosity. The study of the viscosity of polymer melts (43—55) is important for the manufacturer who must supply suitable materials and for the fabrication engineer who must select polymers and fabrication methods. Thus melt viscosity as a function of temperature, pressure, rate of flow, and polymer molecular weight and stmcture is of considerable practical importance. Polymer melts exhibit elastic as well as viscous properties. This is evident in the swell of the polymer melt upon emergence from an extmsion die, a behavior that results from the recovery of stored elastic energy plus normal stress effects. 

The rheological properties of a fluid interface may be characterized by four parameters surface shear viscosity and elasticity, and surface dilational viscosity and elasticity. When polymer monolayers are present at such interfaces, viscoelastic behavior has been observed (1,2), but theoretical progress has been slow. The adsorption of amphiphilic polymers at the interface in liquid emulsions stabilizes the particles mainly through osmotic pressure developed upon close approach. This has become known as steric stabilization (3,4.5). In this paper, the dynamic behavior of amphiphilic, hydrophobically modified hydroxyethyl celluloses (HM-HEC), was studied. In previous studies HM-HEC s were found to greatly reduce liquid/liquid interfacial tensions even at very low polymer concentrations, and were extremely effective emulsifiers for organic liquids in water (6). 

From such microbubble-dissolution measurements, Bemd (ref. 16,17) outlined a physical model to explain much of the dynamic behavior of film-stabilized microbubbles.- One problematic aspect of this dynamic behavior involved the question of how a gas nucleus can be surrounded by a relatively impermeable film and yet subsequently act to produce cavitation when a gas/water interface is needed to initiate cavitation. Bernd (ref. 16) explains that if the stabilized gas microbubble enters a low-pressure area, the gas within the microbubble will attempt to expand. The surfactant film may also elastically attempt to expand. The surfactant film will then be expanded until essentially the surface tension of the water alone acts to contract the microbubble, since the protective shell no longer acts. The film has either been ruptured upon expansion, or it has expanded until it is ineffectual. Thus the microbubble (i.e., gas nucleus) should be capable of expanding to form a cavitation void or acquire additional gas in the form of water vapor or from surrounding dissolved gas. In addition, Bernd points out that it is reasonable to expect a gas microbubble to acquire such an effective... 

A dynamic technique is described for obtaining surface elasticity (e0) vs. surface pressure (tt) curves which can be transformed into accurate tt—A curves for soluble monolayers. Small amplitude periodic area variations are used with a sufficiently high frequency to make monolayers effectively insoluble in the time of the experiment even though they behave as soluble in equilibrium measurements. plots are given for some nonionic surfactants. Straight line portions in these plots illustrate that surface interactions are too complex to be described by a Frumkin isotherm. In the limit of very low surface pressures there is no trace of an ideal gaseous region. Some examples show the implications of particular e0—rr curves for equilibrium and dynamic surface behavior. 

When an aqueous solution of a high-molecular-weight polymer is used in a practical engineering system, the solvent is generally predetermined by the system. However, the importance of the solvent on the pressure drop and heat transfer behavior with these viscoelastic fluids has often been overlooked. Since the heat transfer performance in turbulent flow is critically dependent on the viscous and elastic nature of the polymer solution, it is important to understand the solvent effects on the rheological properties of a viscoelastic fluid. 

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